(a) Technical Field
The present disclosure relates to an integrated coolant flow control and heat exchange device for a vehicle.
(b) Background Art
Generally, a vehicle includes an internal combustion engine, a transmission, a unit heater, a radiator, a pump for delivering a coolant to the engine, and an engine control module. A typical cooling system used in a vehicle includes three main flow circuits: an engine bypass circuit, a circuit including a unit heater, and a circuit including a radiator.
Coolant flow may be controlled by a simple traditional wax pellet fixed temperature thermostat or a more complex coolant control valve with a drive motor, which has been developed as a replacement to the traditional wax pellet type thermostat. The coolant control valve changes coolant flow within circuits based on a signal from a vehicle engine control module unit which is derived from engine coolant temperature.
The coolant control valve reduces engine warm up time by blocking coolant flow at initial cold start and also allowing the engine (coolant and oil) to operate at a higher temperature during normal driving to improve the engine lubricity by controlling the coolant temperature (and engine oil by default) within the engine at higher average temperatures.
The coolant control valve, however, does not provide a more rapid increase in the temperature of the transmission oil circuit because of positional limitation of a transmission oil cooler. More specifically, the transmission oil cooler is typically located in a radiator end tank (i.e., oil to liquid (coolant) type heat exchanger), in the air stream (i.e., air to oil cooler) in front of the vehicle engine cooling module, or both in series depending on transmission cooling demand requirements. Alternatively, it may be provided as a remotely mounted stand alone oil to coolant type cooler.
Such a transmission oil cooler is located within one of the three main flow circuits or an auxiliary circuit. Accordingly, as the coolant flows through multiple coolant circuits, the transmission oil cooler is not fully utilizing the maximum cooling potential available for transmission oil cooling.
Meanwhile, in case where the transmission oil cooler is located in the front end area of the vehicle (either in the radiator tank or air stream), during cold weather driving the transmission oil is typically cooled to the minimum operating temperature if allowed to flow within the heat exchangers provided for cooling. This causes the oil to warm up slowly and can also cause the oil to operate at a temperature which is lower than the temperature for optimum transmission oil lubricity. As a result, more transmission mechanical drag can be caused and vehicle fuel economy during cold weather conditions can be reduced. In case of the air to oil transmission oil cooler, if there is not a temperature bypass valve in the flow circuit, the oil in the cooler can get so cold and thick that the oil cooler may freeze and may not ever allow oil to pass through the cooler and, in some cases, may cause the transmission to be overheated and be damaged due to no oil flow through the transmission oil cooler.
Although devices and systems were proposed to increase the speed of transmission oil warm up, as disclosed in, for example, U.S. Pat. Nos. 6,182,749; 6,371,060; 6,997,143; 6,705,586; 6,796,375; 7,077,776 and 7,168,397, there is still a need for an improved device or system.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.